The objective of this research is to refine the high resolution crystal structure of Cd,Zn metallothionein isoform II from rat liver (MT II). Specifically, this will require: 1. Acquisition of a new data set beyond 2.3 A resolution to 1.5-1.9 A resolution. To facilitate data collection, experiments to further increase the volume of the single crystals will be carried out. 2. Implementation and use of the Hendrickson/Konnert protein refinement program in P4-1-2-1-2 on the Departmental VAX-750 computers, and subsequently, on the new Departmental CONVEX C-1 computer and the new NSF regional Cray supercomputer facility. 3. Refinement of the existing 2.3 A structure against the new data set, with inclusion of water molecules and low-angle solvent correction. Refitting of the structure to residue-deleted, unbiased 2F -F Fourier maps using the program FRODO and the departmental Evans and Sutherland color graphics facility. The objective is to achieve R Less than 0.20 for a model with good stereochemistry. The refined crystal structure will be analyzed with respect to polypeptide stereochemistry, cysteine conformation, metal coordination geometry, hydrogen bonding, and bound solvent molecules and ions. The data will be interpreted in relation to the metal binding properties of metallothioneins in solution. The structure of MT II will be compared to the structure in solution as deduced by two-dimensional NMR methods. A secondary objective is to obtain suitable single crystals of a Cu containing metallothionein (MT) using samples of yeast MT, Nuerospora MT, and the Beta-domain of rat liver MT II reconstituted with Cu (I).